1. Field of the Invention
The present disclosure generally relates to flocculants and methods for flocculating suspended solids. More particularly, the disclosure relates to water in oil emulsions comprising polymeric flocculants and addition of such emulsions to liquids comprising suspended solids.
2. Description of the Related Art
The earth contains deposits of crude oil and bituminous sands, known as tar sands or oil sands. If these deposits are located sufficiently close to the earth's surface, they can be recovered using surface or strip mining techniques. The mined ore typically contains about 10-15% bitumen, 80-85% mineral matter, with the balance being water, and requires separation of the valued bitumen product from the mineral matter.
Separation may be accomplished by initially mixing or slurrying the ore with warm water in a hydrotransport line beginning the bitumen liberation process. The resultant slurry may then be fed to a primary separation vessel or cell. In this process, additional warm water is added and the majority of the liberated bitumen will become attached to air bubbles where it is recovered by flotation. The bitumen liberation and recovery process generally occurs at a pH of about 8.5, which is generally obtained with the assistance of caustic soda. The coarse mineral matter is removed from the bottom of the vessel and a middlings portion, containing water, fine mineral matter and suspended bitumen is sent for further bitumen recovery.
Bitumen may also be diluted with a paraffinic solvent or a naphthenic solvent to aid in the removal of water and mineral matter (clay). Additionally, demulsifiers may be used to enhance the removal of water droplets and solid minerals contained in the water droplets. However, there are completely hydrophobic minerals (generally clay particles that are partially or completely covered by organic components) that cannot be removed by removing the water alone. To remove such minerals, chemical additives have been employed to alter the wettability of the particles from oil-wetted to water-wetted. These techniques have been found to be of limited utility and won't work at all unless there is a bulk water phase present.
Additionally, flocculation techniques may be employed to remove clay minerals. Typically, flocculation of solid particles dispersed in water is accomplished by the use of polymers bearing the opposite charge. However, in low dielectric media, such as aliphatic or aromatic liquids, the particles do not have a strong surface charge and charged polymers having a high molecular weight cannot be dispersed.
High molecular weight (e.g. greater than about 1,000,000 Da) charged polymers are commonly manufactured by polymerizing water soluble monomers that have been dispersed in an oil solvent in the form of a fine emulsion. This causes the polymers to become highly coiled inside the emulsion droplets. To activate the polymers (i.e. uncoil the polymer chains and extend them to expose the charged species), the emulsion is dispersed in very dilute concentrations (typically 0.5% to 2.0% wt.) in water. This dilute polymer solution is then mixed with an aqueous slurry of solids to be flocculated, whereby bridging flocculation occurs due to anchoring of the polymer chains onto the oppositely charged particle surface.